Synopsis
		sfpick < scn.rsf > pik.rsf vel0=o2 niter=100 an=1. gate=3 smooth=y norm=n back=n rect#=(1,1,...) rect1=1 rect2=1 ...

rectN defines the size of the smoothing stencil in N-th dimension.

Theory in Appendix B of:
S. Fomel, 2009,
Velocity analysis using AB semblance: Geophysical Prospecting, v. 57, 311-321.
Reproducible version in RSFSRC/book/tccs/avo
http://ahay.org/RSF/book/tccs/avo/paper_html/

August 2012 program of the month:
http://ahay.org/blog/2012/08/01/program-of-the-month-sfpick/

Parameters
		float an=1. axes anisotropy   bool back=n [y/n] if run backward   int gate=3 picking gate   int niter=100 number of iterations   bool norm=n [y/n] if apply normalization (0.~1.)   int rect#=(1,1,...) smoothing radius on #-th axis   bool smooth=y [y/n] if apply smoothing   float vel0=o2 surface velocity

Used In
		BEI          vela/vscan wvs/vscan   DATA          alaska/line31-81-m8r cant12/lpf cant12/stk freeusp/land nankai/data nankai/shots   DIRACK          examples/modelAndStack examples/pefInterpolation   GEE          prc/bob   GEO384S          hw3/dmo hw3/nmo hw4/alaska hw5/hradon hw5/pradon hw6/gazdag hw6/rtm   GEO384W          hw3/synth hw6/blake   JLU          gvdseisint/ocmodel vdseislet/demultiple vdseislet/nmo vdseislet/usp   M8R          data/freeusp   MILANO          taupvel/cmp   RSF          reprobook/exam3 school/data school/fault school2017/seismic school2020/cmp school2020/seismic scons/rsf tutorials/hilbert   SEP          geostat/dix oc2/elfshot pefmult/mobil vc2/beivc vc2/elfvc vc2/sigvc   TCCS          acrossfault/clyde acrossfault/gulf acrossfault/louis2d acrossfault/synth apwd/trace attr/vecta avo/avo avo/avo2 dealiase2/bei dealiase2/hyper dealiase2/hypern demulemd/mobil diffr/fault diffr/gom dtwaniso/synthetic-gather ltft/vecta merge/apache merge/pcable merge/pcable2 nmodeblend/bei nmodeblend/simple nmodeblend/synth oc3/bei oc3/fault ovc/nankai ovc/psovc pcastack/field phase/boon phase/boon3 phase/nonstat pi/bei pmig/mig probdif/nankai reversible/nscnmo seislet/diplet seislet/gath shape/beivc simistack/bei simistack/flat4 sobel/pari sobel/penobscot sparse/sparse-experim-shaping sparse/vg svmf/bei svmf/class svscan/bei svscan/beicmps svscan/field svscan/simple svscan/synth t2dweak/alaska t2dweak/field time2depth2/beinew timelapse/duri timelapse/long1 timelapse/timelapse uncert/beivc varipick/newviking vscan/bei vscan/hw vscan/stack vscan/synth welllogs/logs welllogs/synthetic-example wetm/beivel wetm/nankaizone   UH          avostack/cmp1 avostack/cmp2 avostack/stack avostack/synh avostack/synl   ZJU          diffrlrra/fault diffrlrra/nankai_new diffrlrra/synth